The other day I was reading the new Tappi Journal, and a business card in the "Supplier Update" section caught my eye. It said "Modular Paper Testing Rooms -Custom-built, Turnkey installations - Guaranteed to meet the TAPPI test atmosphere standard."
Thinking that these modular rooms might be useful in libraries and other collection-holding institutions, I called the company, Environmental Growth Chambers, and spoke with Charlie Briggs (tel: 800/ 321-6854; fax 440-247-87 10). It turns out that these rooms are already being used to provide controlled environments for collections. I talked Mr. Briggs into telling us something about them and describing how they are used in the various institutions that have them. His response follows.E. McCrady, ed.
Since 1952, Environmental Growth Chambers (EGC) has supplied controlled research environments for agricultural, industrial, and government agencies worldwide, from phone-booth size cabinets to rooms 5000 feet square, with precisely controlled setpoints for temperature from below -40°C to over 80°C, and relative humidity from below 2% to over 95%. For me, some of the most interesting are paper testing laboratories ("TAPPI rooms") for companies like Champion Paper and Union Camp; special storage rooms for documents at the Library of Congress and National Archives; and the Evidence Rooms at the new Secret Service Headquarters.
Some characteristics of rooms designed for these purposes are described below.
Insulation . The location and construction of the room should make it possible to maintain a constant wall, floor, and surface temperature close to the desired operating temperature. All surfaces, including ceiling and floor, should be well insulated, finished and sealed.
Special HVAC equipment . Far more than just an adaptation of comfort air conditioning equipment is required. Even units designed to protect electronic data processing equipment are usually inadequate. (Limitations of this kind of equipment include the humidity sensor's lack of sensitivity and inadequate humidification.)
Control of environmental conditions. If the room is too large, temperature control and air distribution could be erratic. If the room is too small, conditions can be adversely affected by human activity, especially when the door is opened. An airlock or vestibule may be required.
We include a mechanical desiccant dryer in the air conditioning system, continuously removing moisture from the air. Then, to bring the moisture up to the desired level, steam from deionized or reverse osmosis water is injected automatically to bring the RH up to the set point.
Temperature and humidity sensors are located inside the room, and are aspirated ; that is, room air is constantly blown over sensors hanging from the ceiling to ensure that representative readings are being made.
Temperature and RH. TAPPI specifies a temperature of 73.4°F ±2° and 50% ±5% RH for paper test room design. Lower values are often used for archival storage. We are
presently doing a 1600 ft2 facility for Brigham Young University Library at 35°-40°F and 30-40% RH.
Refrigeration. The refrigeration system must be able to maintain specified conditions under ambient heat loads, including external air temperature, relative humidity effect, room lighting, and human traffic. EGC uses a microprocessor-controlled direct expansion system, with temperature control through the continuous mixing of liquid and hot-gas phases of refrigerant. Such a design eliminates on-off cycling, and improves both reliability and the controller's response time.
Air changes and circulation. To insure uniformity and close control of conditions, the conditioning equipment will provide 15 to 30 air changes per hour. Large ductwork insures lower velocities, with numerous inlets in the ceiling and air returns located around the periphery, closer to the floor.